Algorithms-for-Information-Retrieval-and-Intelligence-Web_UE20CS332

This repository contains solutions to two assignments:

1. Assignment 1: Implementation of a Search Engine for a given corpus.
2. Assignment 2: Implementation of a Recommender System

Assignment 1: Search Engine Implementation

This assignment involved developing a search engine capable of retrieving relevant information from a corpus of Twitter tweets. The project focused on applying foundational concepts of Information Retrieval, including indexing, querying, and ranking, to provide accurate and efficient search results.

Pre-processing Techniques

1. Case Folding: Converts all characters to lowercase to ensure consistency and reduce redundancy.
2. Tokenization:
   • Sentence Tokenization: Splits text into sentences to preserve contextual meaning.
   • Word Tokenization: Splits sentences into individual words for granular analysis.
3. Stop Word Removal: Removes common words that do not contribute significant meaning.
4. Stemming and Lemmatization:
   • Stemming: Reduces words to their root forms.
   • Lemmatization: Produces meaningful dictionary forms of words.
5. TF-IDF Vectorization: Converts text to numerical form, capturing term importance in a document and across the corpus.

Data Structures Used

1. Dictionary:
   • Used for inverted and positional indexing.
   • Efficient for query intention analysis.
2. Positional Index:
   • Stores document IDs and positions of terms for precise phrase querying.
3. List:
   • Used for n-gram matching in language models.
4. Sparse Matrix:
   • Stores TF-IDF vectors to save memory and optimize similarity computations.

Similarity Scoring Schemes

1. Cosine Similarity: Measures text similarity regardless of document length.
2. Likelihood Scoring: Considers the probability of query terms occurring together in text.

Assignment 2: Recommender System Implementation

This assignment involved developing a Book Recommendation System to suggest books to users based on their interests. The system leverages a dataset of books, user profiles, and ratings to provide personalized recommendations, applying data preprocessing, cleaning techniques, and machine learning concepts to enhance recommendation accuracy.

Data Cleaning and Preprocessing

1. Books Table:

• Removed unnecessary columns (e.g., image URLs).
• Replaced null values and invalid data with appropriate defaults (e.g., mode of publication year).
• Standardized ISBN values.

2. Users Table:

• Replaced invalid ages with the mean of valid ages.
• Split location into city, state, and country columns.

3. Ratings Table:

• Removed invalid and duplicate rows.
• Ensured data consistency with the Books table.

Algorithms Implemented

A. Popularity-Based Recommendations

1. Globally Popular Books: Ranked books by total ratings.
2. Location-Based Popularity: Filtered books by user location and sorted by ratings.
3. Author/Publisher-Based Recommendations: Recommended books by the same author or publisher.
4. Yearly Popular Books: Grouped and ranked books by year of publication.

B. Weighted Average Rating Recommendations

• Used a weighted score formula to recommend books with high overall ratings.

C. Collaborative Filtering

• Built a user-item matrix and used cosine similarity to recommend books.

D. Correlation-Based Recommendations

• Computed a correlation matrix to find similar books.

E. Nearest Neighbor Recommendations

• Trained a Nearest Neighbors model on sparse matrices of user-book ratings.

F. Content-Based Recommendations

• Used TF-IDF feature vectors for unigrams and bigrams of book titles.

G. Hybrid Recommendations

• Combined content-based and collaborative filtering methods for enhanced recommendations.

Libraries Used

• IPython Notebook: For interactive coding.
• scikit-learn: For machine learning models.
• NumPy and SciPy: For numerical operations.
• Pandas: For data manipulation.
• Matplotlib and Seaborn: For data visualization.